Countywide Model of Transport - Hertfordshire...HCC Local Plan data, in line with WebTAG modelling guidance. COMET Model Development The development of COMET has relied upon a wide

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COMETCountywide Model of Transport

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What is COMET?COMET is the Hertfordshire County Model of Transport. COMET has been developed with reference to national guidance, particularly the Department for Transport’s Web Transport Analysis Guidance (WebTAG), and seeks to accord with this guidance where possible in all modelling principles. COMET complements and in some cases supersedes previously used localised models in Hertfordshire and is the key transport planning tool to inform current and future transport patterns and demand across Hertfordshire. Model consists of a Saturn based Highways model and an EMME public transport model linked with a Variable Demand Model.

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COMET Highway and Public Transport NetworksThe COMET highway network covers the Strategic Road Network (SRN), all A-Roads, B-Roads, main C routes (including known ‘rat-runs’), and some minor roads in residential areas. The level of detail is highest within Hertfordshire reducing with distance from the county, corresponding with the level of detail in the zone system.

The adjacent map highlights the motorways, A and B roads contained within the COMET model. As Hertfordshire contains key sections of the M1, A1(M), M25, M11 and A10, Hertfordshire’s significance in catering for strategic as well as local journeys is carefully considered.

Hertfordshire County CouncilCOMET Countywide Model of Transport

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The network used by the COMET public transport model consists of roads, railway lines and pedestrian access routes. The rail and bus network in and around the Hertfordshire area is shown in the adjacent map.

The COMET model zoning system has been created in line with the considerations set out in WebTAG M3.1. There are 1224 zones within the COMET Highway model, with 1040 within Hertfordshire itself. The detail of this zoning system diminishes further from the study area. 50 additional zones are available for testing larger developments in a forecast scenario. The intention with these zones is that they will be moved to represent large developments within the network where the current zone does not suitably represent the characteristics of the proposed development

Hertfordshire County Council COMET Countywide Model of Transport

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Modelled Years and Time PeriodsThe COMET Base Year represents an average weekday in April 2014. Key time periods modelled are 08:00 to 09:00, 10:00 to 16:00 (average hour) and 17:00 to 18:00.

Current COMET Forecast Year scenarios include planning assumptions for 2031 which have been created using the Local Plan aspirations of the 10 Hertfordshire District Councils:

1 2031 Committed Development Scenario – this includes only developments and infrastructure schemes which are currently committed to be built by 2031; and

2 2031 Local Plan Scenario – this includes developments and transport schemes which are currently included within Districts Local Plan aspirations, regardless of certainty.

2031 was chosen as the end point of the majority of Hertfordshire district Local Plans. It is envisaged that the Local Plan scenarios will be updated at least once a year so that the model continues to reflect developing plans. The development of interim year scenarios is also possible, using inputs from the latest National Trip End Model and HCC Local Plan data, in line with WebTAG modelling guidance.

COMET Model DevelopmentThe development of COMET has relied upon a wide range of existing and newly collected data sources. Most notably, COMET makes use of a relatively new technique of incorporating mobile phone data in the development of its highway origin-destination trip matrices. Electronic ticket machine data (ETM) was used for bus services within the model area and station loading figures (from the Office of Rail Regulation) were used for the rail service demand. National Travel Survey (NTS) data, 2011 Census Journey to Work data and Hertfordshire Travel Survey were also used for development of demand matrices.

The COMET Variable Demand Structure is shown in the adjacent figure, detailing how the various elements of the COMET model suite link and interact.

There is a model update programme to ensure that COMET incorporates the latest national planning guidance and meets the latest modelling requirements.


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Model performance The model has been developed following the guiding principles of WebTAG and a full suite of supporting documentation has been produced. Supporting documentation includes the following Technical Notes:

■ Model Coverage and Zoning Structure

■ Traffic Data Collection Specification

■ Hertfordshire County Travel Survey 2015 Collection Recommendations

■ Survey Report – Traffic and Journey Time Data Analysis

■ COMET Highway SATURN Network Coding Manual

■ Matrix Build Process and Validation of Mobile Phone Data

■ Pattern of Travel Across Hertfordshire

■ Public Transport Emme Coding Manual for COMET

■ Bus Data Collection Specification

The model has initially been developed with a focus on the more strategic interurban movements and ongoing model enhancement work is programmed to further enhance the detail and performance of the model in the longer term. On the basis of the model performance so far, appropriate uses of the model are outlined in the following section.

What can COMET be used for?The COMET models were developed to:

■ Identify present and future year highway hotspots / areas of stress; and

■ Be used as a sifting and scenario testing tool for high level assessment of both highway and public transport policy and scheme options.

The COMET Suitability Assessment for the Medium and Long Term in Hertfordshire is shown in the table below.


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Measure Description Can this be tested in COMET? – If No; Recommendation

New Development Growth

Assess the impact of proposed / committed growth across the county’s transport network enabling HCC to locate growth in the right locations and seek necessary developer contributions.

Yes (although individual assessment of small developments may require supplementary local model development and analysis, which COMET can feed into)

Urban Traffic Management Control

Assess the impact of better tactical control strategies for principal highway links.

High Level Assessments Only

Operational assessments will be required using microsimulation modelling for a greater understanding of the impacts. COMET will be able to provide inputs to inform this

New Public Transport Infrastructure

Test the impact of a new public transport scheme e.g. East-West rail or Guided Busway.

Yes but will only be suitable for business case development in the long term.

Public Transport Service Alterations

Impact of changes to public transport services. For example, the impact of removing or increasing service frequency on a corridor.

Yes (the modelling may not be of sufficient detail to consider detailed competition between individual operators within a corridor.)

School Bus Schemes Implementation of School Bus services for pupils.

No It is understood that there is no prospect for School Bus Schemes in Hertfordshire.

New Road Infrastructure Test impact of introducing a new road link such as a bypass.

Yes but will only be suitable for business case development in the long term.

Road Space Reallocation

Dedicated carriageway space for a range of modes and vehicle types, such as new bus lanes, HGV bans and reduction in road space for cycle / pedestrian routes etc.

Suitable at a corridor level

For active mode schemes this will be limited to the agreed highway assignment network detail and the level and quality of available data. Currently it is proposed to use a synthetic matrix in the medium term.

Junction Improvements

Changes to Junction Layouts, signal priorities and capacity enhancements.

High Level Assessments Only. Operational assessments will be required using microsimulation modelling for a greater understanding of the impacts. COMET will be able to provide inputs to inform this.

Road Maintenance / Closure Strategies

Impact of road works and assess the transport network’s resilience to incidents / road closures.

Yes will be able to identify potential re-routeing and diversion route options.


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Measure Description Can this be tested in COMET? – If No; Recommendation

Park-and-ride Implementation of rail, tram and bus-based Park & Ride sites in key corridors. Yes High Level Assessment Only. Developing a business case for such a scheme would require a significant change to the overall approach and higher costs. Therefore this approach should only be considered if Park-and-Ride schemes become a priority in the county.

Parking Management Parking supply management (inc. Park-and-Ride).

Workplace Parking Levy Levy applying to all parking places in a defined area.

Active Mode Schemes Introduction of pedestrian routes and cycle links.

Yes will be suitable at a strategic level for assessing particular policies and provide an early indication on a scheme’s impact / performance. However COMET will not be suitable for developing business cases for specific links. A synthetic matrix will be used for active modes. It is unlikely that there will be access to sufficient data to validate active mode schemes. This is the case across the country.

Smarter Choices

Assess the impact of soft measures such as workplace, school and residential travel plans, personalised travel planning, public transport information and marketing, car clubs, car sharing, Teleworking, teleconferencing, home shopping etc.

Yes if simply implementing valid / defendable demand assumptions to the demand model.

Road User Charging

Charge applied to traffic crossing pre-determined cordons e.g. town centres.

No Understood that this is not a HCC modelling objective. If required, this can be explored in the longer term and could be easily added at a later stage.

Area Wide Accessibility Assessments

Understand travel-times by mode for different areas. For example, do Hertford residents have adequate Public Transport provision to key employment sites across the county?

Yes


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What information can be extracted from COMET?COMET can be used to extract a wide range of information and analysis. One of its primary uses is to compare a number of modelled scenarios to assess the impact of a transport scheme or development. The statistics that indicate overall demand levels by mode of transport can be extracted from the model and analysed.

Outputs can be provided in several outputs including the user-friendly GIS outputs, a summary presentation or a full report, depending on client requirements. In addition to standard model outputs, additional more user friendly analysis can be prepared (see below for some sample outputs) .

These statistics include, but are not limited to:

■ Area highway statistics – total distance travelled, total time taken, average speed, average vehicle delay, mode share statistics;

■ Area public transport statistics for each sub-mode – numbers for boarding and alighting, passenger, distance travelled, total travel time;

■ Highway, public transport and walk/cycle demand matrices – number of trip origins and destinations per model zone and mode;

■ Highway and public transport network statistics showing route and link information such as capacity, distance and journey time;

■ Transport flows crossing defined points, such as city cordons, Rail lines, and screenlines, by direction;

■ With and without mitigation assessments;

■ Development traffic routing analysis and impacts on non-development traffic patterns (eg select link analysis & flow difference plots);

■ Internal/external trip analysis between developments comprising several zones;

■ Impacts on key areas of Hertfordshire – e.g. Highways England network, Air Quality Management Areas and known bottlenecks;

■ Demand information by journey purpose;

■ Trips generated from and attracted to certain areas; and

■ Area Mode Share/Shift


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Example Volume over Capacity Information on Key Arterial Routes (congestion) Plot

Example Junction Delay Information Plot


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Example Public Transport Mode Share Plot Example Volume over Capacity (congestion) Plot


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Example Changes in Journey Times Between Key Urban Areas in Hertfordshire Plot

Example Changes in Interactions Between Key Urban Areas in Hertfordshire Plot


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Example Bus Passenger Flow Change Plot Example Rail Passenger Flow Plot


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Example Summary Statistics Graphs

Example Select Link Analysis GIS Plot

Use of the Model by third parties The COMET model covers the entire County of Hertfordshire and provides a means of assessing the impacts of schemes and /or development on both the highway and passenger transport network. Due to its inclusion of a Variable Demand Model it is also able to indicate impacts such as mode shift and peak spreading.

Third parties wishing to use the model should contact Sue Jackson at Hertfordshire County Council in the first instance ([email protected] tel 01992 588 615) with details of their requirements.

The process to commission COMET modelling work will then be as follows:

■ HCC to send a model test proforma.

■ Third party to confirm via proforma model requirements.

■ HCC to send proforma to their Transport Planning Framework consultants AECOM who will provide a timescale and cost estimate within two weeks of receipt.

■ HCC to apply an additional model maintenance / access charge.

■ Third party to confirm by email that they accept the proposal and provide a PO number for invoicing.

■ AECOM to undertake modelling work providing required outputs within agreed timescales.


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Documents

Countywide Model of Transport - Hertfordshire...HCC Local Plan data, in line with WebTAG modelling guidance. COMET Model Development The development of COMET has relied upon a wide